Ok i am working on a car that was a mess! Most likely the biggest POS EVER....but anyway...its far from that now but theres a problem...the car has massive compressor surge so i loosened the blow off valve up till the idle started to drop and under full throttle theres is no compressor surge...under partial throttle you hear the cha cha cha...but it has a turbosmart BOV and i cant tell if thats the sound of the blow off valve or if its actually still having compressor surge...the car has a EVO 3 Big 16g Turbo.

 

do you have a good vacume source for the bov?

 

yea the vaccum source is circluated right back to the mass airflow sensor where it should be

 

My greddy S BOV makes the same sound under part throttle. It's normal.